1. Field of the Invention
The present invention relates to a process for preparing a rare earth oxide type phosphor. More particularly, it relates to a process for preparing a rare earth oxide type phosphor comprising compressing a starting material for the rare earth oxide type phosphor, followed by firing and pulverizing a compact thereby obtained.
2. Description of the Prior Art
In recent years, a phosphor having a sharp particle size distribution has been desired to obtain a high luminance for a phosphor layer and to improve the coating properties required for forming the phosphor layer. In this respect, it has been common to employ a classification means such as sieving or decantation to remove coarse particles and fine particles from a fired phosphor and thereby to obtain a sharp particle size distribution. However, in such a method, the yield is extremely poor. In order to improve the yield, various researches have been made on the starting materials and fluxes to obtain a fired phosphor which per se has a sharp particle size distribution. However, none of the improvements so far made are totally satisfactory.
Further, it has been a tendency in recent years to employ so-called rare earth phosphors in which rare earth elements are used for the phosphors and which require a high temperature and a long period of time for firing. Costs for the materials and the production costs are thereby extremely high, and due to the above mentioned requirements for the firing, it is difficult to obtain an improved particle size distribution. Under the circumstances, it is strongly desired to improve the yield i.e. to obtain a fired phosphor having a sharp particle size distribution.